Ice Tables

[Matlynn Giles 2E]

How do you know when to have a +X or a -X in an ice table?

[Sean Wang 1F]

When there is an initial concentration, use -x. When the initial concentration is 0, use +x.

[Pranav Daggubati 3C]

It all depends on whether the reaction is proceeding forwards or backward. In other words, you use the K value to see which way the reaction is going and you subtract or add accordingly.

[Anna Martin 2l]

Yes, like said above, it is determined based on initial concentration and as well as if the Q value is bigger or smaller than the K value. If the K value is larger than the Q value, then the reaction favors the forward reaction, where the products are subtracted by X. If the Q is bigger than the K, then the reverse reaction is favored, where the reactants are subtracted by X.

[Sonel Raj 3I]

The simplest way to know is to look at which way the reaction is progressing! If you have an initial concentration for only side of the reaction (either reactants or products), in order to reach equilibrium, you would have to use up a certain amount on that side (-x), and also increase yield on the opposite side of the reaction (+x). Also, remember that x is proportional to the stoichiometric coefficients, so if you have, for example, 2NaOH, be sure to use (2x) rather than just (x).

[Kylie Joe 2A]

Hi! In addition to earlier comments, I like to think of it by looking what is being formed. This way you can know to use +x for the produce or whatever is forming in the reaction, and -x for whatever is being used up, since ultimately you would expect its contents to lessen.

[Crystal Pan 2G]

Depends on the reaction. If concentrations of both products and reactants are given, you could calculate the reaction quotient(Q) and see whether it is small, equal to, or bigger than K. This way you could determine which direction the reaction is proceeding. If only one of the two (R&P) concentrations are given, the reaction is going towards the side that does not have a concentration yet.

[Muskaan Abdul-Sattar]

I was confused about this too! I think as mentioned in other replies, the best way of going about it is checking to see which side has an initial concentration and which side does not. You can assign a -x to the side that has an initial concentration.

[Namratha Gujje]

The way that I have been thinking about it is putting -x when there is a initial concentration value and putting +x when the initial concentration of 0.

[apurva-3E]

reactant / product

[Colin Squire 3B]

The way I think of it is that if I have an initial concentration, I will need to subtract it to create products. On the same point, -x doesn't apply to the products because nothing can be subtracted from zero in the initial row.

[David Jen 1J]

if its a reactant, -x, if its a product, +x

[Edison Tham 3D]

You would have to see how Q compares to K, since when Q<K, the reaction proceeds forward which means that products are forming (thus +x) and reactants are being used (thus -x). When Q>K, the reaction proceeds to the left, meaning that reactants are forming (thus +x) and products are being used (thus -x).

[Jaden Joodi 3J]

It just depends on what way the reaction is going. If it is going away from the products and towards the reactants, it will be -x and +x respectively. (and vice-versa)

[805295074]

It depends if you are given the initial concentration of the reactants or products: if you're given the concentration of reactants, then products are "+x" and reactants are "-x" and vice versa.

[Hannah Lechtzin 1K]

In most instances the compound that you start with will be -x because the reaction will want to form the other compounds involved in the reaction. The compounds that you start off with none of will be +x. Also, make sure that you multiply x by the molar coefficients of each compound.

[Jared Limqueco 3E]

For the basic ones, usually reactants is -x and products is +x, and coefficients depend on the stoichiometric coefficients. But for the more complex ones, you would need to know which side is more favorable to determine which side is -x and +x. So you gotta figure out if Q>k or Q<k.

[Britney Tran IJ]

that depends on the direction that the rxn is proceeding, and you can find that out by comparing q and k

[Jack_Pearce_2H]

Hi!

Use the -x when subtracting from the initial concentration (product or reactant, depends on the problem) given in the problem and add a +x for the molecules produced by the R or P. Add a coefficient of nX when the R or P is (...)^n.

[emwoodc]

you use -x when the reaction is going towards the products and you use +x when the reaction is going towards the reactants

[Aydin Karatas 1F]

If a concentration is given as the initial, that molecule will likely decrease. So use -x for that molecule and all other molecules on that side of the reaction. Molecules on the other side of the reaction will have a +x and have an initial concentration of 0.

[DominicMalilay 1F]

Depending on the reverse or forward reactions, the -x is usually when you already know one of the concentrations while the x is usually for if you don't know the concentrations and are solving for them at first.

[Isaias Gomez D3A]

depends on the initial concentrations given and whether it is a product or reactant. The products get +x and reactants get -x.

[Rose_Malki_3G]

It depends on which way the reaction is moving. If it is going in the forward direction, then it would be -x for the reactants and +x for the products. If the reaction is moving in the reverse direction, then it would be -x for the products and +x for the reactants.

[Mariah Disc 2C]

It depends on which way the reaction is going! If you have an initial concentration in the reactants the -x goes there and the +x goes with the product(s).

[LeahSWM 2E]

It depends whether it is a reactant (-x) or product (+x).

[Melissa Solis 1H]

It can depend on multiple things, the most common reasons are: when there's an initial concentration use -x,0,0. Additionally, the direction is key too; whether the reaction is proceeding backward or forward.

[Armen_Isayan_2L]

Hello! When creating an ICE box, you usually use -x when the concentration is presented as the initial, because that particular molecule will likely decrease, hence that side of the reaction would be represented by -x. On the other hand, the other side of the reaction would be presented by +x.

[Lilly Catarozoli 1B]

You use -x when the reactants are turning into products and +x when the products are forming.